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Lecture 1:

Listen to part of a lecture in a sociology class.

Sociology is really a cross disciplinary field. we find that elements of biology, psychology, and other sciences often overlap as we study particular phenomena. so let me introduce a concept from cognitive psychology. okay? Let’s say someone asks you to look at a list and memorize as many items on it as he can. most of us are able to remember, on average, seven items. there are several variations of this memory test. And the results consistently show that the human limit for short term memory is seven bits of Information. this limit is called channel capacity. shadow capacity is the amount of Information that can be transmitted or received over a specific connection, like our brain and the channel capacity.

For our short term memory. It has some interesting real life implications, like phone numbers. local numbers here in the united states all have seven digits, because the phone companies realized early on that longer numbers would lead to a lot more wrong numbers being dialed. but the idea of channel capacity doesn’t apply just to our cognitive abilities. it also affects our relationships with people around us. psychologists talk about sympathy groups. These are the people, close friends, family to whom we devote the most time. we call or see them frequently.

We think about them, worry about them. And studies show for each of us, the size of that group is about 10 to 15 people. but why so small? sure. Relationships take time and emotional energy. And most of us don’t have unlimited amounts of either.

but what if there’s another reason? what if it’s our brain that setting the limit?

And in fact, there’s evidence that indicates that our social channel capacity may actually be a function of our brain size, or more accurately, the size of our neocortex. the neocortex is the frontal region in the brain of mammals that’s associated with complex thought. primates have the largest neo cortex is among mammals, but among different primate species, humans, apes, baboons, neocortex size varies. A lot of theories have been proposed for these variations. like maybe it’s related to the use of tools, but no theories ever seemed like a perfect explanation. Until the late 1990s, what an anthropologist named robin dunbar published an article about his studies of primates. dunbar theory is that if you look at any particular species of primate, you’ll find that if it has a larger neocortex than it lives in a larger social group, take human beings. We have the largest neocortex a sand. We have the largest number of social relationships. so we’ve said that our sympathy group is 10 to 15 people. What about our other relationships other than family?

And close friends, such as those that occur in the workplace will call these social groups as opposed to sympathy groups? how many relationships can we handle there? those relationships aren’t as involved, so we can handle more of them. but is there an upper limit? well, dunbar says that there is, and he developed an equation to calculate it. his equation depends on knowing the ratio between the size of the neocortex and the size of the whole brain that is of the whole brain. What percentage of it is taken up by the neo cortex? once you know the average percentage for any particular species, the equation predicts the expected maximum social group size for that species. for humans, that number seems to be about 150.

so according to dunn bars equation, our social groups probably won’t number more than 150 people. now, dunbar hypothesis isn’t the kind of thing that’s easy to confirm in a controlled experiment, but there is anecdotal evidence to support it. as part of his research, dunbar reviewed historical records for 21 different traditional hunter gatherer societies. and those records showed that the average number of people in each village was just under 150 hundred hundred and 48.4, to be exact.

done bars also worked with biologists to see if his hypothesis applies to other mammals besides primates.

When they looked at meat eating mammals, carnivores, they found that the ones with a larger neocortex also have a bigger social group. and the number of individuals in that group is predicted by done bars equation supporting his hypothesis. but when they looked at insect of wars, mammals that eat insects, the results were inconsistent. the data didn’t disprove dunbar hypothesis, but it wasn’t a nice, neat match like the carnivore studies, which isn’t totally surprising.

insectivore oars are hard to observe, since many of them only come out at night or they spend a lot of time underground. So we know a lot less about their social relationships.

nd for all the same reasons.